<?php

/**
 * 数据库备份与还原请求接口
 */

class backup {
	private $database;
	private $db;
	/**
	 * 文件指针
	 * @var resource
	 */
	private $fp;

	/**
	 * 备份文件信息 part - 卷号，name - 文件名
	 * @var array
	 */
	private $file;

	/**
	 * 当前打开文件大小
	 * @var integer
	 */
	private $size = 0;

	/**
	 * 备份配置
	 * @var integer
	 */
	private $config;

	/**
	 * 数据库备份构造方法
	 * @param array  $file   备份或还原的文件信息
	 * @param array  $config 备份配置信息
	 * @param string $type   执行类型，export - 备份数据， import - 还原数据
	 */
	public function __construct($file, $config, $type = 'export'){
		$this->database = pc_base::load_config('database');
		$this->database = $this->database['default'];
		$this->db = new PDO('mysql:host=' . $this->database['hostname'] . ';dbname=' . $this->database['database'] . '; port=' . $this->database['port'], $this->database['username'], $this->database['password'], array(PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION));
		$this->file   = $file;
		$this->config = $config;
	}

	/**
	 * 打开一个卷，用于写入数据
	 * @param  integer $size 写入数据的大小
	 */
	private function open($size){
		if($this->fp){
			$this->size += $size;
			if($this->size > $this->config['part']){
				$this->config['compress'] ? @gzclose($this->fp) : @fclose($this->fp);
				$this->fp = null;
				$this->file['part']++;
				param::set_session('backup_file', $this->file);
				$this->create();
			}
		} else {
			$backuppath = $this->config['path'];
			$filename   = "{$backuppath}{$this->file['name']}-{$this->file['part']}.sql";
			if($this->config['compress']){
				$filename = "{$filename}.gz";
				$this->fp = @gzopen($filename, "a{$this->config['level']}");
			} else {
				$this->fp = @fopen($filename, 'a');
			}
			$this->size = filesize($filename) + $size;
		}
	}

	/**
	 * 写入初始数据
	 * @return boolean true - 写入成功，false - 写入失败
	 */
	public function create(){
		$sql  = "-- -----------------------------\n";
		$sql .= "-- MySQL Data Transfer \n";
		$sql .= "-- \n";
		$sql .= "-- Host     : " . $this->database['hostname'] . "\n";
		$sql .= "-- Port     : " . $this->database['port'] . "\n";
		$sql .= "-- Database : " . $this->database['database'] . "\n";
		$sql .= "-- \n";
		$sql .= "-- Part : #{$this->file['part']}\n";
		$sql .= "-- Date : " . date("Y-m-d H:i:s") . "\n";
		$sql .= "-- -----------------------------\n\n";
		$sql .= "SET FOREIGN_KEY_CHECKS = 0;\n\n";
		return $this->write($sql);	
	}

	/**
	 * 写入SQL语句
	 * @param  string $sql 要写入的SQL语句
	 * @return boolean     true - 写入成功，false - 写入失败！
	 */
	private function write($sql){
		$size = strlen($sql);

		//由于压缩原因，无法计算出压缩后的长度，这里假设压缩率为50%，
		//一般情况压缩率都会高于50%；
		$size = $this->config['compress'] ? $size / 2 : $size;

		$this->open($size); 
		return $this->config['compress'] ? @gzwrite($this->fp, $sql) : @fwrite($this->fp, $sql);
	}

	/**
	 * 备份表结构
	 * @param  string  $table 表名
	 * @param  integer $start 起始行数
	 * @return boolean        false - 备份失败
	 */
	public function backup($table, $start){
		//备份表结构
		if(0 == $start){
			$sth = $this->db->prepare("SHOW CREATE TABLE `{$table}`");
			$sth->execute();
			$result = $sth->fetchAll(PDO::FETCH_ASSOC);
			$sql  = "\n";
			$sql .= "-- -----------------------------\n";
			$sql .= "-- Table structure for `{$table}`\n";
			$sql .= "-- -----------------------------\n";
			$sql .= "DROP TABLE IF EXISTS `{$table}`;\n";
			$sql .= trim($result[0]['Create Table']) . ";\n\n";
			//dump($this->write($sql));die;
			if(false === $this->write($sql)){
				return false;
			}
		}

		$sth = $this->db->prepare("SELECT * FROM `{$table}`");
		$sth->execute();
		$c_rows = $sth->columnCount();

		//数据总数
		$sth = $this->db->prepare("SELECT COUNT(*) AS count FROM `{$table}`");
		$sth->execute();
		$result = $sth->fetchAll(PDO::FETCH_ASSOC);
		$count  = $result['0']['count'];

		//备份表数据
		if($count){
			//写入数据注释
			if(0 == $start){
				$sql  = "-- -----------------------------\n";
				$sql .= "-- Records of `{$table}`\n";
				$sql .= "-- -----------------------------\n";
				$this->write($sql);
			}

			//备份数据记录
			$result = $this->db->query("SELECT * FROM `{$table}` LIMIT {$start}, 1000");
			foreach ($result as $row) {
				$sql = "REPLACE INTO `{$table}` VALUES (";
				$cdata = array();
				for ($i = 0; $i < $c_rows; $i++) {
					if (is_null($row[$i])) {
						$cdata[] = "null";
					} else {
						$new_lines = $this->escape($row[$i]);
						$cdata[] = "'" . $new_lines . "'";
					}
				}
				$sql .= implode(', ', $cdata);
				$sql .= ");\n";
				if(false === $this->write($sql)){
					return false;
				}
			}

			//还有更多数据
			if($count > $start + 1000){
				return array($start + 1000, $count);
			}
		}

		//备份下一表
		return 0;
	}

	public function import($start){
		//还原数据
		if($this->config['compress']){
			$this->fp   = gzopen($this->file[1], 'r');
			$size = 0;
		} else {
			$size = filesize($this->file[1]);
			$this->fp   = fopen($this->file[1], 'r');
		}

		$sql  = '';
		if($start){
			$this->config['compress'] ? gzseek($this->fp, $start) : fseek($this->fp, $start);
		}

		for($i = 0; $i < 1000; $i++){
			$sql .= $this->config['compress'] ? gzgets($this->fp) : fgets($this->fp); 
			if(preg_match('/.*;$/', trim($sql))){
				if(false !== $this->db->query($sql)){
					$start += strlen($sql);
				} else {
					return false;
				}
				$sql = '';
			} elseif ($this->config['compress'] ? gzeof($this->fp) : feof($this->fp)) {
				return 0;
			}
		}

		return array($start, $size);
	}

	public function escape($str){
		$str = $this->db->quote($str);
		return ($str[0] === "'") ? substr($str, 1, -1) : $str;
	}

	/**
	 * 析构方法，用于关闭文件资源
	 */
	public function __destruct(){
		$this->config['compress'] ? @gzclose($this->fp) : @fclose($this->fp);
	}
}